Shackleton’s modus operandi is described as “brand-building campaigns that combine award-winning creative work with a dedicated focus on digital customer engagement”. Its clients include the likes of Uber and Spanish train operator Renfe, and it has won awards including 35 Cannes Lions.

Alzugaray, Shackleton’s chief executive and co-founder, said the deal would “increase our capacity to do better work for brands”.

He added: “If we joined one of the traditional advertising holdings, we would access more of what we already are.

“In contrast, Accenture brings us much of what we are not. Advanced technology, applied intelligence, cognitive robotic, big and small data, extended reality, the Internet of Things… will take the strategic and creative capacity of our team to create brand experiences to an unknown dimension in conventional advertising.”